Finance departments hate tracking "sub-capacity" licensing. With unlimited, you stop counting. There is no "true-up" audit at the end of the year. You pay one price and stop worrying about concurrent usage reports.
By default, OpenVPN AS comes with (perfect for testing). Beyond that, you purchase "Connected User Licenses" or "Device Licenses" in bundles (e.g., 10, 25, 50, 100, 250, 500, or 1000+). openvpn access server license unlimited
Typical use cases